A variety of abnormal passages called fistulas can occur in humans. Such fistulas may be caused by, for example, an infection, a congenital defect, inflammatory bowel disease (such as Crohn's disease), irradiation, trauma, neoplasia, childbirth, or a side effect from a surgical procedure.
Some fistulas occur between the vagina and the bladder (vesico-vaginal fistulas) or between the vagina and the urethra (urethro-vaginal fistulas). These fistulas may be caused by trauma during childbirth. Traditional surgery for these types of fistulas is complex and not very successful.
Other fistulas include, but are not limited to, tracheo-esophageal fistulas, gastro-cutaneous fistulas, fistulas extending between the vascular and gastrointestinal systems, and any number of anorectal (ano-cutaneous) fistulas, such as fistulas that form between the anorectum and vagina (recto-vaginal fistulas), between the anorectum and bladder (recto-vesical fistulas), between the anorectum and urethra (recto-urethral fistulas), or between the anorectum and prostate (recto-prostatic fistulas). Anorectal fistulas can result from infection in the anal glands, which are located around the circumference of the distal anal canal forming an anatomic landmark known as the dentate line 1, shown in FIGS. 1 and 2. Approximately 20-30 such glands are found in humans. Infection in an anal gland can result in an abscess. This abscess can then track through soft tissues (e.g., through or around the sphincter muscles) into the perianal skin, where it drains either spontaneously or surgically. The resulting void through the soft tissue is known as a fistula. The internal or inner opening of the fistula, usually located at or near the dentate line, is known as the primary opening 2. The primary opening is usually the high pressure end of a fistula. Any external or outer openings, which are usually located in the perianal skin, are known as the secondary openings 3. The secondary openings are usually the low pressure end of a fistula.
FIGS. 1 and 2 show examples of the various paths that an anorectal fistula may take. These paths vary in complexity. Fistulas that take a straight line path from the primary opening 2 to the secondary opening 3 are known as simple fistulas 4. Fistula that contain multiple tracts ramifying from the primary opening 2 and have multiple secondary openings 3 are known as complex fistulas 5.
The anatomic path that an anorectal fistula takes is classified according to its relationship to the anal sphincter muscles 6, 7. The anal sphincter includes two concentric bands of muscle: the inner, or internal, sphincter 6 and the outer, or external, sphincter 7. Fistulas which pass between the two concentric anal sphincters are known as inter-sphincteric fistulas 8. Those which pass through both internal 6 and external 7 sphincters are known as trans-sphincteric fistulas 9, and those which pass above both sphincters are called supra-sphincteric fistulas 10. Fistulas resulting from Crohn's disease usually ignore these anatomic paths, and are known as extra-anatomic fistulas.
Many complex fistulas contain multiple tracts, some blind-ending 11 and others leading to multiple secondary openings 3. One of the most common and complex types of fistulas is known as a horseshoe fistula 12. In this instance, the infection starts in the anal gland (the primary opening 2) at or near the twelve o'clock location (with the patient in the prone position). From this primary opening, fistulas pass bilaterally around the anal canal, in a circumferential manner, forming a characteristic horseshoe configuration 12, as illustrated in FIG. 2. Multiple secondary openings 3 from a horseshoe fistula 12 may occur anywhere around the periphery of the anal canal, resulting in a fistula tract with a characteristic horseshoe configuration 12.
One technique for treating a fistula is to make an incision adjacent the anus until the incision contacts the fistula and then excise the fistula from the anal tissue. This surgical procedure tends to sever the fibers of the anal sphincter, and may cause incontinence.
Another technique for treating a fistula involves passing a fistula probe through the tract, in a blind manner, using primarily only tactile sensation and experience to guide the probe. Having passed the probe through the fistula tract, the overlying tissue is surgically divided. This is known as a fistulotomy. Because a variable amount of sphincter muscle is divided during the procedure, fistulotomy may result in impaired sphincter control or even incontinence. Alternative methods and instruments, such as coring-out instruments (See, e.g., U.S. Pat. Nos. 5,628,762 and 5,643,305), may make the fistula wider and more difficult to close.
Yet another technique for treating a fistula involves draining infection from the fistula tract and maturing it prior to a definitive closure or sealing procedure by inserting a narrow diameter rubber drain, known as a seton, through the tract. This is usually accomplished by inserting a fistula probe through the outer (secondary) opening 3 and gently guiding it through the fistula, and out through the inner (primary) opening 2. A seton, thread or tie is then affixed to the tip of the probe, which is then withdrawn back out of the tract, leaving the thread in place. The seton may then be tied as a loop around the contained tissue and left for several weeks or months.
An additional method of closing the primary opening is by surgically creating a flap of skin, drawing this flap of skin across the opening, and suturing the flap in place. This procedure (the endo-anal flap procedure) closes the primary opening, but is technically difficult to perform, is painful for the patient, and is associated with a high fistula recurrence rate.
More recently, methods have evolved to inject sclerosant or sealant (e.g., collagen or fibrin glue) into the tract of the fistula to block the fistula. Such sealants are described in Rhee, U.S. Pat. No. 5,752,974, for example. Usually, multiple injections are required to close the fistula by this method. In some instances, closure of a fistula using a sealant may be performed as a two-stage procedure, comprising a first-stage seton placement, followed by injection of the fibrin glue several weeks later. This procedure reduces residual infection and allows the fistula tract to “mature” prior to injecting a sealant. Injecting sealant or sclerosant into an unprepared or infected fistula as a one-stage procedure can cause a flare-up of the infection and even further abscess formation.
Even more recently, methods of treating fistulas by placing a graft in the fistula tract have been discovered, as described in co-pending application serial number 11/040,996 (Armstrong), U.S. Patent Application Publication No. 2006/0074447, hereby incorporated by reference in its entirety. Such grafts may have a tapered body with a wider proximal end and a thinner distal end, as shown in FIG. 3. The graft may be pulled through the primary opening until the head portion of the graft is lodged in the primary opening, where it is retained in the same manner as a plug in a hole. The graft may also be secured by suturing the graft to the tissue of the patient, for example. Despite the tapering design of these grafts, they may still be subject to displacement or extrusion from the patient when excessive force is applied to the proximal end of the graft during exertion or straining, especially in the case of the wide fistulas that are common in patients with Crohn's disease or recto-vaginal fistulas. Although suture may be used to further secure the graft in some instances, it may be difficult to suture the proximal end of the graft to the tissues of a patient where surgical access to the primary opening of the fistula is limited, such as in anorectal and recto-vaginal fistulas where the primary opening is often located high in the rectum. Even if suturing the graft to the tissues of a patient is possible, the suturing may be painful for the patient.
Other techniques for treating fistulas are described in U.S. application Ser. No. 11/415,403, titled “VOLUMETRIC GRAFTS FOR TREATMENT OF FISTULAE AND RELATED METHODS AND SYSTEMS” (Cook Biotech Incorporated), filed May 1, 2006, which claims priority to U.S. Provisional Application Ser. No. 60/676,118, filed Apr. 29, 2005; and U.S. Provisional Application (Ser. No. not yet assigned), titled “FISTULA GRAFTS AND RELATED METHODS AND SYSTEMS USEFUL FOR TREATING GASTROINTESTINAL FISTULAE” (Cook Biotech Incorporated), filed Jun. 21, 2006, naming F. Joseph Obermiller as the inventor, which are hereby incorporated by reference in their entirety.
There remains a need for improved and/or alternative medical products, methods, and systems that are useful for treating fistulas. The present invention addresses these needs.